The present invention pertains to vehicle accessories with electrical options and more particularly, to ambient light sensors for vehicle accessories.
Vehicles are often provided with a variety of accessories. One popular vehicle accessory is an electrically adjustable rearview mirror which responds to sensed light, such as the headlights from a trailing vehicle, to change the reflectivity of the rearview mirror for glare reduction. Electrical adjustment of these mirrors is typically provided by a prism mirror having two reflective states or an optical transmission plate with electrically controlled optical properties. Regardless of whether a prism mirror or an optical plate is used to control the mirror reflectivity, these mirrors include a control circuit which generates an electrical control signal. The electrical control signal is applied to a motor of a prism mirror or the optical transmission plate. The control signal is generated as a function of one or more ambient light levels which are typically detected by two light sensors. A rearward light sensor detects the ambient light level in front of the rearview mirror (toward the rear of the vehicle) and a forward light sensor detects the ambient light level behind the rearview mirror (toward the front of the vehicle).
A difficulty presented by electrically adjustable rearview mirrors is accommodating the rearward facing light sensor. The rearward facing sensor typically includes a photo-sensor with a light responsive surface facing the rear of the vehicle. The photo-sensor is sometimes mounted in a mirror housing to receive light through an optical opening in the reflective surface of the rearview mirror. However, this discontinuity in the rearview mirror surface may partially obstruct the vehicle operator's vision behind the vehicle. Alternatively, it is known to mount the light sensor in a sensor housing below the mirror housing. The sensor housing includes an opening facing the rear of the vehicle which passes light onto a photo-sensor supported within the sensor housing. Although the photo-sensor housing does not obstruct the driver's vision behind the vehicle, it requires electrical conductors which extend between the photo-sensor and an electrical circuit board which is typically carried in the mirror housing. Assembling the sensor housing to a rearview mirror housing can be costly due to the labor and materials required to connect the sensor and the rearview mirror electrical circuit board and to construct and attach the sensor housing to the rearview mirror housing. Such construction also provides another potential area for a defect to occur.